Bone Microarchitecture in Transgender Adults: A Cross-Sectional Study

Gender-affirming hormone therapy aligns physical characteristics with an individual's gender identity, but sex hormones regulate bone remodeling and influence bone morphology. We hypothesized that trans men receiving testosterone have compromised bone morphology because of suppression of ovarian estradiol production, whereas trans women receiving estradiol, with or without anti-androgen therapy, have preserved bone microarchitecture. We compared distal radial and tibial microarchitecture using high-resolution peripheral quantitative computed tomography images in a cross-sectional study of 41 trans men with 71 cis female controls, and 40 trans women with 51 cis male controls. Between-group differences were expressed as standardized deviations (SD) from the mean in age-matched cisgender controls with 98% confidence intervals adjusted for cross-sectional area (CSA) and multiple comparisons. Relative to cis women, trans men had 0.63 SD higher total volumetric bone mineral density (vBMD; both p = 0.01). Cortical vBMD and cortical porosity did not differ, but cortices were 1.11 SD thicker (p < 0.01). Trabeculae were 0.38 SD thicker (p = 0.05) but otherwise no different. Compared with cis men, trans women had 0.68 SD lower total vBMD (p = 0.01). Cortical vBMD was 0.70 SD lower (p < 0.01), cortical thickness was 0.51 SD lower (p = 0.04), and cortical porosity was 0.70 SD higher (p < 0.01). Trabecular bone volume (BV/TV) was 0.77 SD lower (p < 0.01), with 0.57 SD fewer (p < 0.01) and 0.30 SD thicker trabeculae (p = 0.02). There was 0.56 SD greater trabecular separation (p = 0.01). Findings at the distal radius were similar. Contrary to each hypothesis, bone microarchitecture was not compromised in trans men, perhaps because aromatization of administered testosterone prevented bone loss. Trans women had deteriorated bone microarchitecture either because of deficits in microstructure before treatment or because the estradiol dosage was insufficient to offset reduced aromatizable testosterone. Prospective studies are needed to confirm these findings. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

High Luteinizing Hormone and Lower Levels of Sex Hormones in Younger Men With Distal Radius Fracture

This study investigates the sex steroid hormone profile in younger men with distal radius fracture (DRF) to elucidate if this could explain the low bone density and osteoporosis previously observed. In a case-control study, 73 men with DRF (mean age 38 ± 9 years; range, 20-51) was compared with 194 age-matched, population controls. Performed assays: total testosterone (TT), calculated free testosterone (cFT), luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), and total estradiol (E2). BMD hip and spine were measured. Fracture cases had lower cFT (298 versus 329 pmol/L; p = 0.008), but not TT, compared with controls. FSH and SHBG were not statistically different. LH was almost 30% higher (5.7 versus 4.5 IU/L; p < 0.001) and a lower E2 was observed (80.0 versus 87.1; p = 0.098). Men with DRF had a lower E2/SHBG ratio compared with controls (2.3 versus 2.9; p = 0.013). A higher proportion of the fracture group had low TT (<10.5 nmol/L; 21% versus 11%; p = 0.052), low cFT (<220 pmol/L; 18% versus 8%; p = 0.017), and low E2 (<73 pmol/L; 48% versus 35%; p = 0.044). Odds ratio (OR) for fracture when having low cFT was 2.3 (95% CI, 1.02-5.49; p = 0.044); with low E2, the OR was 1.7 (95% CI, 0.96-2.96). In this study in young men with DRF exploring sex hormone levels, we find that sex hormone profiles may be disturbed with a lower E2/SHBG ratio, lower cFT, and higher LH. Estrogen is also a strong determinant of bone mass in men; hence, low levels of E2 may be contributing to the observed lower BMD and these differences may be relevant to fracture risk. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Estradiol and Follicle-Stimulating Hormone as Predictors of Onset of Menopause Transition-Related Bone Loss in Pre- and Perimenopausal Women

The menopause transition (MT) may be an opportunity for early intervention to prevent rapid bone loss. To intervene early, we need to be able to prospectively identify pre- and perimenopausal women who are beginning to lose bone. This study examined whether estradiol (E2), or follicle-stimulating hormone (FSH), measured in pre- and perimenopausal women, can predict significant bone loss by the next year. Bone loss was considered significant if bone mineral density (BMD) decline at the lumbar spine (LS) or femoral neck (FN) from a pre- or early perimenopausal baseline to 1 year after the E2 or FSH measurement was greater than the least detectable change. We used data from 1559 participants in the Study of Women's Health Across the Nation and tested E2 and FSH as separate predictors using repeated measures modified Poisson regression. Adjusted for MT stage, age, race/ethnicity, and body mass index, women with lower E2 (and higher FSH) were more likely to lose BMD: At the LS, each halving of E2 and each doubling of FSH were associated with 10% and 39% greater risk of significant bone loss, respectively (p < 0.0001 for each). At the FN, each halving of E2 and each doubling of FSH were associated with 12% (p = 0.01) and 27% (p < 0.001) greater risk of significant bone loss. FSH was more informative than E2 (assessed by the area under the receiver-operator curve) at identifying women who were more versus less likely to begin losing bone, especially at the LS. Prediction was better when hormones were measured in pre- or early perimenopause than in late perimenopause. Tracking within-individual change in either hormone did not predict onset of bone loss better than a single measure. We conclude that measuring FSH in the MT can help prospectively identify women with imminent or ongoing bone loss at the LS. © 2019 American Society for Bone and Mineral Research.

27-Hydroxycholesterol, an Endogenous SERM, and Risk of Fracture in Postmenopausal Women: A Nested Case-Cohort Study in the Women's Health Initiative

27-Hydroxycholesterol (27HC) is a purported, novel endogenous SERM. In animal models, 27HC has an anti-estrogen effect in bone, and 17β-estradiol mitigates this effect. 27HC in relation to fracture risk has not been investigated in humans. Depending on the level of bioavailable 17β-estradiol (bioE₂ ), 27HC may increase fracture risk in postmenopausal women and modify the fracture risk reduction from menopausal hormone therapy (MHT). To test these a priori hypotheses, we conducted a nested case-cohort study of 868 postmenopausal women within the Women's Health Initiative Hormone Therapy (WHI-HT) trials. The WHI-HT tested conjugated equine estrogens versus placebo and separately conjugated equine estrogens plus progestin versus placebo. Fracture cases were 442 women who had an adjudicated incident hip or clinical vertebral fracture during the WHI-HT follow-up. The subcohort included 430 women randomly selected at WHI-HT baseline, four of whom had a subsequent fracture. Of the 868 women, 266 cases and 219 non-cases were assigned to the placebo arms. Cox models estimated hazard ratios for incident fracture in relation to pre-randomization circulating levels of 27HC and 27HC/bioE₂ molar ratio. Models adjusted for age, race/ethnicity, total cholesterol, bioE₂ , sex hormone-binding globulin, 25-hydroxyvitamin D, diabetes, osteoporosis, prior MHT use, BMI, falls history, and prior fracture. In women assigned to placebo arms, those in the middle and the highest tertiles of 27HC/bioE₂ had an up to 1.9-fold (95% confidence intervals, 1.25 to 2.99) greater risk of fracture than women in the lowest tertile. In women assigned to MHT arms, fracture risk increased with continuous 27HC/bioE₂ levels but not with categorical levels. 27HC levels alone were not associated with fracture risk. 27HC and 27HC/bioE₂ did not modify the fracture risk reduction from MHT. In postmenopausal women, circulating levels of 27HC relative to bioE₂ may identify those at increased risk of fracture. © 2018 American Society for Bone and Mineral Research.

The Skeleton Is a Storehouse of Mineral That Is Plundered During Lactation and (Fully?) Replenished Afterwards

During lactation, mammals resorb mineral from the maternal skeleton to provide calcium to milk. Rodents lose 25% to 35% of skeletal ash weight, ash calcium content, and bone mineral content as measured by dual-energy X-ray absorptiometry (DXA), and have compromised material properties of bone as assessed by crushing vertebrae and 3-point bend tests of femora or tibias. The strength, stiffness, and toughness of vertebrae, femora, and tibias are reduced by as much as 60%. The effects of lactation are not uniform throughout the skeleton, but instead resorption is much more marked in the trabecular-rich spine than in the appendicular skeleton or whole body. Women who breastfeed exclusively lose an average of 210 mg calcium in milk each day, whereas nursing of twins or triplets can double and triple the output of calcium. Clinical data are also consistent with skeletal calcium being released during lactation to provide much of the calcium needed for milk production. Lumbar spine bone mineral density (BMD), as assessed by DXA, declines by a mean of 5% to 10% among numerous studies during 3 to 6 months of exclusive lactation, whereas largely cortical sites (hip, forearm, whole body) show half that loss or no significant changes. Micro-CT of rodents and high-resolution peripheral quantitative computed tomography (HR-pQCT) imaging of women confirm that lactation causes microarchitectural deterioration of bone. These skeletal losses occur through two pathways: upregulated osteoclast-mediated bone resorption and osteocytic osteolysis, in which osteocytes remove mineral from their lacunae and pericanalicular spaces. After weaning, the skeleton is fully restored to its prior mineral content and strength in both animal models and humans, despite persistent microarchitectural changes observed in high-resolution imaging. Osteoblasts upregulate to lay down new osteoid, while osteocytes remineralize their surroundings. The factors that stimulate this post-weaning skeletal recovery remain unclear. In most studies, a history of lactation does not increase the risk, but may protect against, low BMD and fragility fractures. © 2017 American Society for Bone and Mineral Research.

MicroRNA-19b reduces hepatic stellate cell proliferation by targeting GRB2 in hepatic fibrosis models in vivo and in vitro as part of the inhibitory effect of estradiol

Estradiol (E2) is a major determinant of gender-based differences in the development of hepatic fibrosis. MicroRNAs (miRNAs) are endogenous 19-25 nucleotide, noncoding, single-stranded RNAs that regulate gene expression by blocking the translation or decreasing the stability of mRNAs and play an important role in liver fibrosis. The mechanisms underlying the regulation of miRNAs by E2 remain largely unknown. In this study, miR-19b levels were higher and were associated with lower GRB2 mRNA and protein levels in female rats more than in male rats. We also showed that miR-19b levels were down-regulated, were associated with the up-regulation of GRB2 mRNA and protein levels in PS (porcine serum-induced hepatic fibrosis) versus NS (normal control) groups and were up-regulated when associated with the down-regulation of GRB2 mRNA and protein levels in PS + E2 versus PS and in aHSC + E2 (estradiol treated aHSC) versus aHSC groups. MiR-19b expression inhibited cell proliferation in aHSCs, and also down-regulated GRB2 protein expression. The overexpression of miR-19b inhibited cell growth and suppressed COL1A1 protein levels by decreasing the levels of GRB2. However, the forced expression of GRB2 partly rescued the effect of miR-19b in the cells, attenuated cell proliferation, and suppressed the GRB2 protein level by up-regulating the levels of GRB2. Taken together, these findings will shed light on the role of miR-19b in regulating aHSC proliferation via the miR-19b/GRB2 axis. This newly identified miR-19b/GRB2 interaction provided novel insights into the suppressive effect of E2 on HSC proliferation and might facilitate the development of therapies targeting hepatic fibrosis.

The 1,25D3 -MARRS receptor/PDIA3/ERp57 and lifespan

Using MRI on mice bearing a targeted knockout (KO) of the 1,25D3 -MARRS receptor/PDIA3/ERp57 we found that they had decreased body fat relative to their littermate (LM) controls, a condition associated with increased lifespan. Others have found that lower body fat is correlated with decreased lipid droplets in intestinal cells that may be mediated by a factor secreted by germ cells (possibly estradiol). In a reducing environment estradiol competed for binding to the 1,25D3-MARRS receptor/PDIA3/ERp57. A consequence of this was that estradiol stimulated calcium uptake in enterocytes isolated from LM mice. In time course studies, lipid droplets increased in response to 1 nM estradiol from 1-5 D of culture, relative to corresponding controls, while at 6 and 7 D this steroid decreased lipid droplets. Enterocytes from LM or KOs incubated with estradiol for 1-4 D showed the hormone increased lipid droplets. Using the 4 D culture period, 1 and 10 nM estradiol significantly increased the number of lipid droplets in cells from LM mice by 40-60%, compared to equivalent conditions in KO mice. In assessing signal transduction pathways, the hormone increased phospho-Akt levels, but no differences were observed in phospho-mTORC1, or phospho-S6K (although cells from chicks did exhibit a hormone-mediated difference). Finally, the remaining mice (which had stopped reproducing) were allowed to die naturally and lifespan recorded. LM mice lived 687 ± 77 D (without an outlying value) while KO mice lived 740 D ± 80 D. These data suggest the 25D3 -MARRS receptor/PDIA3/ERp57 may contribute to the length of lifespan in mammals.

Inhibition of synthesis of sulfated mucopolysaccharides by estradiol

The influence of estradiol upon incorporation of isotopes into the sulfated acid mucopolysaccharides of connective tissues of the rat has been studied. Administration of the hormone for 3 weeks significantly reduces the in vitro incorporation of S³⁵-sulfate into cartilage and thoracic aorta without significantly altering the amount of hydrolyzable sulfate in these tissues. The reduction of sulfate incorporation into these tissues by estradiol represents reduced synthesis since the hormone reduces incorporation of sulfate into the acid mucopolysaccharides of the tissue to the same extent and since reduction in incorporation of C¹⁴-glucose also parallels S³⁵-sulfate incorporation into acid mucopolysaccharides. The rate of synthesis of sulfated acid mucopolysaccharides is greater in thoracic aorta than abdominal aorta or cartilage. Since the amount of hydrolyzable sulfate is the same in these two portions of aorta, the turnover is also more rapid in the thoracic aorta.

Interactions of oestrogens and androgens on the mammary gland and growth of other tissues in hypohysectomized rats treated with insulin, cortisone and thyroxine

In a previous study it was found that oestrogens are necessary for androgens to elicit a development of alveolar lobules in the mammary glands of rats. Since androgens and oestrogens exert synergistic as well as antagonistic actions on mammary glands of e. g. rabbits, the significance of oestrogens in the response of the mammary gland to androgens was further investigated in the rat. The experiments were designed according to the same principles as previously, that is, the response of the gland itself to oestrogens was modified. This was achieved by treatment of hypophysectomized rats with a) thyroxine (negligible response) and b) thyroxine, cortisone and insulin (marked response). The effect of endogenous androgens was studied in males injected with PMS with or without oestrogens. Gonadectomized rats were injected with testosterone and oestrogens.

DNA SYNTHESIS IN ALVEOLAR CELLS OF THE MAMMARY GLAND: ACCELERATION BY OVARIAN HORMONES

In normal alveolar cells of the mammary gland of C3H/HeJ female mice, DNA synthesis lasts an average of 20.7 hours with a coefficient of variation of 26.6 percent. Treatment of the mice with I microgram of 17-beta-estradiol and 1 milligram of progesterone per day for 3 to 4 days decreases the average duration to 10.7 hours and the coefficient of variation to 13.8 percent.

URINARY VOLUME AND EXCRETION OF OESTROGENS IN LATE PREGNANCY

The relationship between urinary volume and oestrone, 17β-oestradiol and oestriol was studied initially within the range of spontaneous variation and subsequently with the aid of water loads and diuretics. The spontaneous variations in urinary output showed no definite correlation with the excretion of oestrogens, while massive hydration led to increased excretion. With hydrochlorothiazide a clear positive correlation was obtained. The authors regard the results as evidence in favour of the view that reabsorption of the above-mentioned oestrogens occurs in the region of the proximal tubules.

METABOLITES OF TRITIATED TESTOSTERONE IN HEALTHY MEN

Tracer doses of tritiated testosterone were injected into four healthy men, followed by urine collection and by an assay for estrone, estradiol, androsterone, etiocholanolone, dehydroepiandrosterone, and Δ16-androstenol, and by an assay for radioactivity in each of these fractions. The androstenol fraction contained very little tritium, which indicated that most of it was not derived from the miscible testosterone pool. Maximum testosterone production rates were calculated from the urinary estrone and estradiol data, the results indicating testosterone turnovers of 1 to 3 mg per day. Comparison with testosterone production rates for healthy men, which were reported by other investigators using different methods, indicated that most, if not all, of the estrone and estradiol produced by the four subjects was derived from the miscible testosterone pool.

OESTRADIOL METABOLISM IN THE PREVIABLE HUMAN FOETUS AND IN THE FOETO-PLACENTAL UNIT

Five normal previable foetuses were perfused with tracer amounts of oestradiol-4-14C and the metabolism of the compound was investigated. This study was completed by 3 experiments in which the oestradiol-4-14C was introduced in situ into the intact foeto-placental unit via the umbilical circulation.

More than 80 per cent of the radioactive material present in the various foetal organs in both types of experiments was in a conjugated form. In contrast, in the placentas, less than 10 per cent of the total radioactivity present was in a conjugated form.

The bulk of the radioactive material present in the foetal tissues was identified as oestradiol 3-sulphate and oestrone sulphate. In addition, two minor fractions were detected in the perfused foetuses, one of which behaved in countercurrent distribution studies as »glucosiduronates«; the other resembled »sulphates«. The oestrogen moiety of these two fractions was neither oestradiol nor oestrone, but it appeared to be a complex mixture. Although some radioactive material was found which closely resembled oestriol, it was not possible to detect oestriol with certainty.

No glucosiduronate-like material was found in the foetal tissues following the injection of oestradiol-4-14C into the intact foeto-placental unit. Also the quantity of the »sulphate-like« material different from oestradioland oestrone sulphates was greatly reduced:

A number of unconjugated metabolites were also detected, among which oestrone was identified.

A perfusion experiment with an anencephalic foetus indicated that this foetus was capable of forming conjugated metabolites from oestradiol-4-14C.

The results obtained do not favour the view that oestriol is a major and instantaneously formed foetal metabolite of oestradiol. On the other hand, they lend additional support to the concept that oestrogens reaching the foetus are extensively sulphurylated by the foetus and that these oestrogen sulphates are hydrolysed by the placenta before transfer of the oestrogen moiety to the maternal circulation.

THE INHIBITION OF TWO STEROID-ACTIVATED NICOTINAMIDE-ADENINE DINUCLEOTIDE (PHOSPHATE) TRANSHYDROGENASES BY FOLIC ACID AND FOLIC ACID ANTIMETABOLITES

1. It was found that steroid-mediated nicotinamide-adenine dinucleotide (phosphate) transhydrogenases can be inhibited in vitro by folic acid and its antimetabolites. The most potent inhibitor was methotrexate, a drug with a high therapeutic index against experimental cancer. 2. The inhibitions produced by a combination of folic acid and the analogues were additive, as were those between the folic acid compounds and antagonistic steroid hormones.

RECOVERY OF GONADAL FUNCTION IN MALE RATS TREATED NEONATALLY WITH 17 BETA-OESTRADIOL BENZOATE

Groups of five day old rats were injected with 120 or 240 μg of oestradiol benzoate. When examined at the age of fifty days, the animal presented atrophied testes and marked decreases in the weights of ventral prostate, seminal vesicles and levator ani muscle. Treatment with pregnant mare's serum or with testosterone propionate given from day 20 through day 50 fully restored the gonadal activity. The dose of PMS needed to restore spermatogenesis was 10 IU which was given every third day. Testosterone propionate, 1 mg, given daily was equally effective.

EFFECTS OF OVARIECTOMY AND OF HORMONES ON COLLAGENOUS FRAMEWORK OF THE UTERUS

Alterations in the size of the collagenous framework of the uterine horns of the rat under different physiological conditions have been examined by mechanical tests in which they were distended in vitro with Locke's solution, containing papaverine to prevent muscular activity, under pressure which was increased progressively until they burst. This framework was found to show large and rapid changes in size related to the endocrine state of the animal. It was larger in estrus and diestrus and reduced by ovariectomy. Its size was increased by relaxin in combination with progesterone and estradiol and by the latter substance alone.

THE SYNTHESIS OF PHOSVITIN IN VITRO BY SLICES OF LIVER FROM THE LAYING HEN

1. Slices of liver from laying hens incorporated Na(2) (14)CO(3) and NaH(2) (32)PO(4) into phosvitin. Slices of liver from immature birds did not do so to any appreciable extent. The (32)P was incorporated into O-phosphorylserine in the phosvitin molecule. 2. Kidney, spleen, muscle, large and small intestine, ovary and oviduct from laying birds did not incorporate Na(2) (14)CO(3) into phosvitin. 3. Slices of liver from laying hens carried out a net synthesis of phosphoprotein under the standard conditions of incubation. Slices from the livers of immature pullets did not do so. 4. Liver from the laying hen incorporated [2-(14)C]glycine, [3-(14)C]serine and [2-(14)C]glutamic acid into phosvitin. Part of the glycine was shown to be present as serine in the final product. 5. Slices of liver from immature birds treated with oestradiol synthesized phosvitin from [2-(14)C]glycine, but the addition of oestrogens in vitro to slices from untreated immature birds did not promote synthesis during a 3 hr. incubation period.

LOBULOALVEOLAR DIFFERENTIATION IN MOUSE MAMMARY TISSUES IN VITRO

Administration of lobuloalveolar mammogenic hormones (for a period insufficient to induce alveolar differentiation) to immature mice prior to cultivation of their mammary glands in chemically defined, hormone-supplemented media resulted in lobuloalveolar growth in vitro comparable to that of late pregnancy. No such growth occurred in cultures of mammary tissues from mice not treated with hormones. The use of tissues from hormone-treated donors might serve as a valuable tool for studies concerned with differentiation in vitro.